The present invention relates to a method for preparing alkane sulfonyl halides. More particularly, this invention concerns a method for producing higher-alkane sulfonyl chlorides through the oxidation of alkyl mercaptans or dialkyl disulfides while inhibiting the formation of undesirable byproducts.
Alkane sulfonyl halides, particularly alkane sulfonyl chlorides, are know for their utility in imparting functionality into various compounds or as intermediates to modify various compounds, including pharmaceuticals, agriculture chemicals, photographic chemicals and the like, in order to increase their efficacy, to protect sensitive functional groups during certain processing steps, or to improve the recovery and purity during isolation procedures.
A number of prior-art methods are known for preparing alkane sulfonyl halides, particularly methane sulfonyl chloride. A known preparation process for methane sulfonyl chloride involves the reaction of chlorine with methyl mercaptan or dimethyl disulfide in an aqueous solution of hydrogen chloride. The products of such reaction generally include methane sulfonyl chloride, hydrogen chloride, and at least one undesirable byproduct.
When methyl mercaptan or dimethyl disulfide is employed as a reactant to produce a methane sulfonyl halide, the amount of undesirable byproducts is minimal. However, when higher-alkyl mercaptans or higher-alkyl disulfides are employed as reactants to produce higher-alkane sulfonyl halides, the quantity of undesirable byproducts, such as alpha-chlorinated byproducts, is greatly increased. The presence of such undesirable byproducts causes the process to be less efficient and can necessitate the implementation of expensive separation processes and equipment.
An object of the present invention is to provide a more efficient process for preparing higher-alkane sulfonyl halides.
A further object of the present invention is to provide a process for preparing higher-alkane sulfonyl halides which inhibits the formation of at least one undesirable byproduct.
Other objects and advantages of the present invention will become more apparent as the invention is more fully disclosed hereinbelow.
In accordance with the present invention, there is provided a process for preparing higher-alkane sulfonyl halides comprising contacting a sulfur-containing compound, a halogen-containing compound, and a phase transfer agent within a reaction zone under conditions sufficient to produce a higher-alkane sulfonyl halide.
As used herein, the term xe2x80x9chigher-alkanexe2x80x9d means an alkane having 2 or more carbon atoms, preferably 2 to 20 carbon atoms.
It has been discovered that, in a process for producing higher-alkane sulfonyl halides by reacting a sulfur-containing compound and a halogen-containing compound, the presence of a phase transfer agent during such reaction inhibits the production of certain undesirable byproducts.
Thus, in accordance with an embodiment of the present invention, a sulfur-containing compound, a halogen-containing compound, and phase transfer agent are contacted within a reaction zone under reaction conditions sufficient to produce a higher-alkane sulfonyl halide.
The sulfur-containing compound employed in the process of the present invention can generally be represented by the formula RSX, wherein X is hydrogen or a radical of the formula SR1 and where R is an alkyl group having 2 to 20 carbon atoms, preferably 3 to 12 carbon atoms, and R1 is an alkyl group having 1 to 20 carbon atoms, preferably 1 to 12 carbon atoms. R and R1 can be the same or different alkyl groups, but are preferably the same. The alkyl groups may be branched or straight-chained and may also be substituted alkyl radicals having such substituent atoms and groups as hydroxyl, chlorine, bromine, fluorine, amine (NH2), sulfonic acid (SO3H), sulfonyl chloride (SO2Cl), and SO3R. However, the alkyl groups are preferably not substituted directly with halogens. More preferably, both alkyl groups, R and Rxe2x80x2, are unsubstituted.
Preferred sulfur-containing compounds include ethyl mercaptan, n-propyl mercaptan, isopropyl mercaptan, n-butyl mercaptan, n-hexyl mercaptan, cyclohexyl mercaptan, n-octyl mercaptan, n-nonyl mercaptan, n-decyl mecaptan, n-dodecyl mercaptan, diethyl disulfide, di-n-propyl disulfide, di-iso-propyl disulfide, di-n-butyl disulfide, di-iso-butyl disulfide, di-n-hexyl disulfide, di-iso-hexyl disulfide, di-n-octyl disulfide, di-iso-octyl disulfide, and combinations of any two or more thereof. More preferably, the sulfur-containing compound is n-propyl mercaptan, n-octyl mercaptan, di-n-propyl disulfide, di-n-octyl disulfide or a combination of two or more thereof. Most preferably, the sulfur-containing compound is n-octyl mercaptan.
The halogen-containing compound employed in the process of the present invention can be any halogen-containing compound suitable for reacting with the sulfur-containing compound to produce the desired alkane sulfonyl halide product of this invention. Preferably, the halogen of the halogen-containing compound is chlorine or bromine, but more preferably it is chlorine. Most preferably, the halogen-containing compound is chlorine (Cl2).
The amount of halogen-containing compound employed in the process of the present invention can be the stoichiometric amount suitable for reacting with the sulfur-containing compound to yield the desired alkane sulfonyl halide. Generally, the weight ratio of halogen-containing compound to sulfur-containing compound employed in the present inventive process is from about 1:10 to about 100:1, but can be from about 1:2 to about 20:1, or from about 1:1 to about 8:1, or from 2:1 to 4:1.
The sulfur-containing compound and halogen-containing compound are preferably contacted within a reaction zone in the presence of an aqueous hydrogen halide. Preferably, the aqueous hydrogen halide comprises hydrochloric acid, hydrobromic acid, or a mixture thereof. Most preferably, the aqueous hydrogen halide comprises hydrochloric acid. The weight of the hydrogen halide as a percentage of the total weight of the aqueous hydrogen halide is preferably from about 5 weight percent to about 80 percent, more preferably from about 10 to about 50 percent, more preferably from about 20 to about 40 percent, most preferably from 25 to 35 percent.
The amount of aqueous hydrogen halide employed in the process present invention can be any amount which is effective to produce the desired alkane sulfonyl halide product. Preferably, the amount of aqueous hydrogen halide is such that the weight ratio of the hydrogen halide in the aqueous hydrogen halide to the sulfur-containing compound is from about 1:25 to about 50:1, more preferably from about 1:5 to about 10:1, and most preferably from 1:3 to 6:1.
Generally, the phase transfer agent employed in the process of the present invention comprises one or more compounds capable of inhibiting the formation of undesirable byproducts and promoting the yield of desired sulfonyl halide.
A preferred phase transfer agent for use in the reaction system of the instant invention is selected from the group consisting of alkoxylated compounds, quaternary ammonium salts, alkali metal alkyl sulfates, alkali metal salts of alkanoic acids, alkali metal salts of alkaryl sulfonic acids, 1-alkyl pyridinium salts, and combinations of two or more thereof.
The presently preferred phase transfer agent is an alkoxylated compound. Examples of suitable alkoxylated compounds include, but are not limited to, alkoxylated alcohols, alkoxylated mercaptans, sulfates of alkoxylated alcohols, alkoxylated phenols, sulfates of alkoxylated phenols, and combinations of two or more thereof.
An alkoxylated alcohol useful in the present invention has a general formula of R2O[CH2CH(R3)O]qH where R2 is a C1-C20 hydrocarbyl radical selected from the group consisting of alkyl radical, alkylaryl radical, aryl radical, cycloalkyl radical, alkenyl radical, and combinations of two or more thereof, preferably R2 is a C6-C18 alkyl radical, most preferably R2 is a C10-C16 alkyl radical; R3 is selected from the group consisting of hydrogen, C1-C16 alkyl radicals, C2-C16 alkenyl radicals, and combinations of two or more thereof, preferably R3 is a hydrogen or a C1-C3 alkyl radical, most preferably R3 is hydrogen; and q is an integer of from 1 to about 20, preferably from about 2 to about 12, most preferably from 5 to 10. An example of suitable alkoxylated alcohol is TERGITOL(copyright) 15-S-7. TERGITOL(copyright) 15-S-7 is an ethoxylated alcohol, manufactured and marketed by Union Carbide Corporation, having the formula of R2O(CH2CH2O)7H where R2 is a secondary alkyl radical having 11-15 carbon atoms and 7 is the averaged number of the ethylene oxide units. Other suitable alkoxylated alcohols are also available from Union Carbide Corporation.
A sulfate of alkoxylated alcohol useful in the present invention has a general formula of R2O[CH2CH(R3)O]qSO3M where R2, R3, and q are the same as those described above and M is an alkali metal or an alkaline earth metal or combinations of two or more thereof. An example of suitable sulfate of alkoxylated alcohol is sodium sulfate of an ethoxylated alcohol having the formula of R2O(CH2CH2O)qSO3Na in which R2 and q are the same as those disclosed above.
Useful alkoxylated phenols and sulfates of alkoxylated phenols can have general formulas of (R3)pArO[CH2CH(R3)O]qH and (R2)pArO[CH2CH (R3)O]]qSO3M, respectively where R2, R3, q and M are the same as those disclosed above, Ar is an aryl group, preferably a phenyl group, and p is an integer ranging from 0 to 5. Examples of these alkoxylated phenols are ethoxylated phenol ArO(CH2CH2O)qH and sodium sulfate of ethoxylated phenol ArO(CH2CH2O)qSO3 Na where Ar and q are the same as disclosed above.
An alkoxylated mercaptan useful in the present invention has a general formula of R2S[CH2CH(R3)O]qH where R2, R3, and q are the same as those described above. An example of an alkoxylated mercaptan is an ethoxylated mercaptan having the formula of R2S(CH2CH2O)7H where R2 is primarily a tertiary dodecyl group and 7 is the averaged number of ethylene oxide units. This ethoxylated mercaptan is a surfactant, available under the trade name AQUA-CLEEN(copyright)II (Phillips Petroleum Company, Bartlesville, Okla.). Another example is an ethoxylated thiophenol having the same number of ethylene oxide units. Other suitable alkoxylated mercaptans are also available from Phillips Petroleum Company.
Quaternary ammonium salts useful in the present invention have the general formula (R4)4N+Xxe2x88x92 where R4 is an alkyl radical of from 1 to 20 carbon atoms; and X is selected from the group consisting of Brxe2x88x92, Clxe2x88x92, Ixe2x88x92, Fxe2x88x92, R4CO2xe2x88x92, QSO3xe2x88x92, BF4xe2x88x92, and HSO4xe2x88x92, where Q is an aryl, alkaryl or arylalkyl radical of 6 to 10 carbon atoms. It will be noted that a variety of anions are suitable as the component of the quaternary ammonium salts.
Useful quaternary ammonium salts according to the general formula given above include, but are not limited to, methyltrialkyl(C8-C10) ammonium chloride (also known as ADOGEN 464 (copyright), Aldrich Chemical Company), cetyltrimethylammonium bromide, hexadecyltrimethylammonium bromide, tetraheptylammonium bromide, cetyltrimethylammonium stearate, benzyltributylammonium chloride, benzyltriethylammonium bromide, benzyltrimethylammonium bromide, phenyltrimethylammonium bromide, phenyltrimethylammonium iodide, tetrabutylammonium bromide, tetrabutylammonium chloride, tetrabutylammonium hydrogen sulfate, tetrabutylammonium iodide, tetraethylammonium bromide, tetrabutylammonium fluoride, tetrabutylammonium tetrafluoroborate, and combinations of two or more thereof.
An alkali metal alkyl sulfate of the general formula of R4OSO3M can be used in the present invention, wherein R4 and M are the same as those disclosed above. Examples of suitable compounds according to the general formula for the alkali metal alkyl sulfates include, but are not limited to, lithium decylsulfate, potassium dodecylsulfate, sodium dodecylsulfate, sodium hexadecylsulfate, potassium hexadecylsulfate, rubidium dodecylsulfate, cesium dodecylsulfate, sodium octadecylsulfate, potassium octadecylsulfate, potassium eicosylsulfate, sodium eicosylsulfate, and combinations of two or more thereof.
Useful alkali metal salts of alkanoic acids have the general formula of R4CO2M, where R4 and M have the same meaning as given above. Examples of suitable alkali metal salts of alkanoic acids include, but are not limited to, lithium decanoate, sodium dodecanoate, potassium dodecanoate, rubidium dodecanoate, cesium dodecanoate, sodium hexadecanoate, potassium hexadecanoate, sodium octadecanoate, potassium octadecanoate, sodium eicosanoate, potassium eicosanoate, and combinations of two or more thereof.
Useful alkali metal salts of alkaryl sulfonic acids have the general formula of (R4)pArSO3M where R4 and M are the same as those disclosed above, Ar is an aryl group or a phenyl group, and p is an integer ranging from 0 to 5. Typical compounds within such group include, but are not limited to, sodium dodecylbenzenesulfoante, potassium dodecylbenzenesulfonate, lithium dodecylbenzenesulfonate, sodium tetradecylbenzenesulfonate, potassium hexadecylbenzenesulfoante, rubidium dodecylbenzenesulfoante, cesium dodecylbenzenesulfonate, sodium octadecylbenzenesulfoante, potassium octadecylbenzenesulfonate, soidum eicosylbenzenesulfonate, and combinations of two or more thereof.
Examples of suitable 1-alkyl pyridinium salts include, but are not limited to, 1-dodecylpyridinium para-toluenesulfonate, 1-dodecylpyridinium chloride, 1-hexadecylpyridinium chloride, 1-hexadecylpyridinium paratoluenesulfonate, 1-decylpyridinium chloride, 1-hexadecylpyridinium bromide, 1-tetradecylpyridinium chloride, 1-octadecylpyridinium chloride, 1-eicosylpyridinium chloride, 1-octadecylpyridinium benzenesulfonate, and combinations of two or more thereof.
The amount of the phase transfer agent employed in the present inventive process can be any amount which inhibits the formation of undesirable byproducts and/or promotes the formation of the desired sulfonyl halide. Preferably, the amount of phase transfer agent employed gives a weight ratio of phase transfer agent to sulfur-containing compound of from about 1:1,000 to about 1:1, preferably from about 1:500 to about 1:3, and most preferably from 1:300 to 1:5.
The sulfur-containing compound, halogen-containing compound, and phase transfer agent can be contacted in any suitable reaction vessel. The contacting conditions can be any conditions sufficient to produce the desired alkane sulfonyl halide. Usually, the reaction is carried out at substantially atmospheric pressure, while either atmospheric pressure or reduced pressure may be used in the purification steps. The reaction temperature is generally from about xe2x88x9210xc2x0 C. to about 50xc2x0 C., preferably from about 25xc2x0 C. to about 35xc2x0 C. The process can be carried out either batchwise or continuously.
The product produced by the process of the present invention comprises a higher-alkane sulfonyl halide. Preferably, the higher-alkane sulfonyl has the formula RSO2Y, wherein Y is chlorine or bromine, preferably chlorine; and R is an alkane having 2 to 20 carbon atoms, more preferably 3-12 carbon atoms, and most preferably 8 carbon atoms. Preferred higher-alkane sulfonyl halides include propane sulfonyl chloride, butane sulfonyl chloride, hexane sulfonyl chloride, octane sulfonyl chloride, nonane sulfonyl chloride, decane sulfonyl chloride, dodecane sulfonyl chloride, and combinations of two or more thereof. Most preferably, the higher-alkane sulfonyl halide is octane sulfonyl chloride.
The product produced by the present invention may further comprise at least one undesirable by product; however, the amount of such byproduct in the product produced by the present inventive process is less than the amount of such byproduct in a product produced when a phase transfer agent, such as those used in the inventive process, is not used. The undesirable byproduct whose formation is inhibited by the process of the present invention can be, for example, an alpha-chlorinated compound, generally an alpha-chloroalkane sulfonyl halide corresponding to the desired higher-alkane sulfonyl halide product.
The product of the present inventive process may be subjected to further recovery, separation, and purification processes known in the art in order to recover a substantially pure higher-alkane sulfonyl halide product.
The following example is provided to further illustrate the practice of the present invention and is not intended to limit the scope of the invention of the claims.